The Dewatering of Lime-Algae Sludge on Sand Drying Beds,

摘要

Removal of algae from stabilization pond effluents is required for the effluent to meet current federal discharge standards. Application of a thickened lime-algae sludge to sand drying beds was investigated as a treatment method. The sludge was loaded at rates of 4.0to 16.1gal/sq ft to sand bed columns with media depths of 6to 12inches. A sludge cake with an average 25% solids content was obtained within ten hours at bed depths of 6to 10inches over the loadings applied,while 65hours were required for a bed depth of 12inches at loadings above 12gal/sq ft. Investigations indicated that dewatering rate and effluent quality were not related to media size from 0.3to 1.5mm. Dewatering rates decreased with increasing solids loading from about 1to 6lbs/sq ft;however,effluent quality and sludge cake solids did not appear to be affected by solids loading. Dewatering rates above 1gal/sq ft/hr were noted at a bed depth of 10inches. Effluent suspended solids from the drying beds averaged 100mg/l. Supernate withdrawal significantly decreased the dewatering time at the 12-inch bed depth;however,the supernate averaged 175mg/l of total suspended solids,which would require recirculation to the lagoon.